drivers/net/caif/caif_serial.c

   1 /*
   2  * Copyright (C) ST-Ericsson AB 2010
   3  * Author:      Sjur Brendeland / sjur.brandeland@stericsson.com
   4  * License terms: GNU General Public License (GPL) version 2
   5  */
   6
   7 #include <linux/hardirq.h>
   8 #include <linux/init.h>
   9 #include <linux/module.h>
  10 #include <linux/device.h>
  11 #include <linux/types.h>
  12 #include <linux/skbuff.h>
  13 #include <linux/netdevice.h>
  14 #include <linux/rtnetlink.h>
  15 #include <linux/tty.h>
  16 #include <linux/file.h>
  17 #include <linux/if_arp.h>
  18 #include <net/caif/caif_device.h>
  19 #include <net/caif/cfcnfg.h>
  20 #include <linux/err.h>
  21 #include <linux/debugfs.h>
  22
  23 MODULE_LICENSE("GPL");
  24 MODULE_AUTHOR("Sjur Brendeland<sjur.brandeland@stericsson.com>");
  25 MODULE_DESCRIPTION("CAIF serial device TTY line discipline");
  26 MODULE_LICENSE("GPL");
  27 MODULE_ALIAS_LDISC(N_CAIF);
  28
  29 #define SEND_QUEUE_LOW 10
  30 #define SEND_QUEUE_HIGH 100
  31 #define CAIF_SENDING            1 /* Bit 1 = 0x02*/
  32 #define CAIF_FLOW_OFF_SENT      4 /* Bit 4 = 0x10 */
  33 #define MAX_WRITE_CHUNK      4096
  34 #define ON 1
  35 #define OFF 0
  36 #define CAIF_MAX_MTU 4096
  37
  38 /*This list is protected by the rtnl lock. */
  39 static LIST_HEAD(ser_list);
  40
  41 static bool ser_loop;
  42 module_param(ser_loop, bool, S_IRUGO);
  43 MODULE_PARM_DESC(ser_loop, "Run in simulated loopback mode.");
  44
  45 static bool ser_use_stx = true;
  46 module_param(ser_use_stx, bool, S_IRUGO);
  47 MODULE_PARM_DESC(ser_use_stx, "STX enabled or not.");
  48
  49 static bool ser_use_fcs = true;
  50
  51 module_param(ser_use_fcs, bool, S_IRUGO);
  52 MODULE_PARM_DESC(ser_use_fcs, "FCS enabled or not.");
  53
  54 static int ser_write_chunk = MAX_WRITE_CHUNK;
  55 module_param(ser_write_chunk, int, S_IRUGO);
  56
  57 MODULE_PARM_DESC(ser_write_chunk, "Maximum size of data written to UART.");
  58
  59 static struct dentry *debugfsdir;
  60
  61 static int caif_net_open(struct net_device *dev);
  62 static int caif_net_close(struct net_device *dev);
  63
  64 struct ser_device {
  65         struct caif_dev_common common;
  66         struct list_head node;
  67         struct net_device *dev;
  68         struct sk_buff_head head;
  69         struct tty_struct *tty;
  70         bool tx_started;
  71         unsigned long state;
  72         char *tty_name;
  73 #ifdef CONFIG_DEBUG_FS
  74         struct dentry *debugfs_tty_dir;
  75         struct debugfs_blob_wrapper tx_blob;
  76         struct debugfs_blob_wrapper rx_blob;
  77         u8 rx_data[128];
  78         u8 tx_data[128];
  79         u8 tty_status;
  80
  81 #endif
  82 };
  83
  84 static void caifdev_setup(struct net_device *dev);
  85 static void ldisc_tx_wakeup(struct tty_struct *tty);
  86 #ifdef CONFIG_DEBUG_FS
  87 static inline void update_tty_status(struct ser_device *ser)
  88 {
  89         ser->tty_status =
  90                 ser->tty->stopped << 5 |
  91                 ser->tty->flow_stopped << 3 |
  92                 ser->tty->packet << 2 |
  93                 ser->tty->port->low_latency << 1;
  94 }
  95 static inline void debugfs_init(struct ser_device *ser, struct tty_struct *tty)
  96 {
  97         ser->debugfs_tty_dir =
  98                         debugfs_create_dir(tty->name, debugfsdir);
  99         if (!IS_ERR(ser->debugfs_tty_dir)) {
 100                 debugfs_create_blob("last_tx_msg", S_IRUSR,
 101                                 ser->debugfs_tty_dir,
 102                                 &ser->tx_blob);
 103
 104                 debugfs_create_blob("last_rx_msg", S_IRUSR,
 105                                 ser->debugfs_tty_dir,
 106                                 &ser->rx_blob);
 107
 108                 debugfs_create_x32("ser_state", S_IRUSR,
 109                                 ser->debugfs_tty_dir,
 110                                 (u32 *)&ser->state);
 111
 112                 debugfs_create_x8("tty_status", S_IRUSR,
 113                                 ser->debugfs_tty_dir,
 114                                 &ser->tty_status);
 115
 116         }
 117         ser->tx_blob.data = ser->tx_data;
 118         ser->tx_blob.size = 0;
 119         ser->rx_blob.data = ser->rx_data;
 120         ser->rx_blob.size = 0;
 121 }
 122
 123 static inline void debugfs_deinit(struct ser_device *ser)
 124 {
 125         debugfs_remove_recursive(ser->debugfs_tty_dir);
 126 }
 127
 128 static inline void debugfs_rx(struct ser_device *ser, const u8 *data, int size)
 129 {
 130         if (size > sizeof(ser->rx_data))
 131                 size = sizeof(ser->rx_data);
 132         memcpy(ser->rx_data, data, size);
 133         ser->rx_blob.data = ser->rx_data;
 134         ser->rx_blob.size = size;
 135 }
 136
 137 static inline void debugfs_tx(struct ser_device *ser, const u8 *data, int size)
 138 {
 139         if (size > sizeof(ser->tx_data))
 140                 size = sizeof(ser->tx_data);
 141         memcpy(ser->tx_data, data, size);
 142         ser->tx_blob.data = ser->tx_data;
 143         ser->tx_blob.size = size;
 144 }
 145 #else
 146 static inline void debugfs_init(struct ser_device *ser, struct tty_struct *tty)
 147 {
 148 }
 149
 150 static inline void debugfs_deinit(struct ser_device *ser)
 151 {
 152 }
 153
 154 static inline void update_tty_status(struct ser_device *ser)
 155 {
 156 }
 157
 158 static inline void debugfs_rx(struct ser_device *ser, const u8 *data, int size)
 159 {
 160 }
 161
 162 static inline void debugfs_tx(struct ser_device *ser, const u8 *data, int size)
 163 {
 164 }
 165
 166 #endif
 167
 168 static void ldisc_receive(struct tty_struct *tty, const u8 *data,
 169                         char *flags, int count)
 170 {
 171         struct sk_buff *skb = NULL;
 172         struct ser_device *ser;
 173         int ret;
 174         u8 *p;
 175
 176         ser = tty->disc_data;
 177
 178         /*
 179          * NOTE: flags may contain information about break or overrun.
 180          * This is not yet handled.
 181          */
 182
 183
 184         /*
 185          * Workaround for garbage at start of transmission,
 186          * only enable if STX handling is not enabled.
 187          */
 188         if (!ser->common.use_stx && !ser->tx_started) {
 189                 dev_info(&ser->dev->dev,
 190                         "Bytes received before initial transmission -"
 191                         "bytes discarded.\n");
 192                 return;
 193         }
 194
 195         BUG_ON(ser->dev == NULL);
 196
 197         /* Get a suitable caif packet and copy in data. */
 198         skb = netdev_alloc_skb(ser->dev, count+1);
 199         if (skb == NULL)
 200                 return;
 201         p = skb_put(skb, count);
 202         memcpy(p, data, count);
 203
 204         skb->protocol = htons(ETH_P_CAIF);
 205         skb_reset_mac_header(skb);
 206         skb->dev = ser->dev;
 207         debugfs_rx(ser, data, count);
 208         /* Push received packet up the stack. */
 209         ret = netif_rx_ni(skb);
 210         if (!ret) {
 211                 ser->dev->stats.rx_packets++;
 212                 ser->dev->stats.rx_bytes += count;
 213         } else
 214                 ++ser->dev->stats.rx_dropped;
 215         update_tty_status(ser);
 216 }
 217
 218 static int handle_tx(struct ser_device *ser)
 219 {
 220         struct tty_struct *tty;
 221         struct sk_buff *skb;
 222         int tty_wr, len, room;
 223
 224         tty = ser->tty;
 225         ser->tx_started = true;
 226
 227         /* Enter critical section */
 228         if (test_and_set_bit(CAIF_SENDING, &ser->state))
 229                 return 0;
 230
 231         /* skb_peek is safe because handle_tx is called after skb_queue_tail */
 232         while ((skb = skb_peek(&ser->head)) != NULL) {
 233
 234                 /* Make sure you don't write too much */
 235                 len = skb->len;
 236                 room = tty_write_room(tty);
 237                 if (!room)
 238                         break;
 239                 if (room > ser_write_chunk)
 240                         room = ser_write_chunk;
 241                 if (len > room)
 242                         len = room;
 243
 244                 /* Write to tty or loopback */
 245                 if (!ser_loop) {
 246                         tty_wr = tty->ops->write(tty, skb->data, len);
 247                         update_tty_status(ser);
 248                 } else {
 249                         tty_wr = len;
 250                         ldisc_receive(tty, skb->data, NULL, len);
 251                 }
 252                 ser->dev->stats.tx_packets++;
 253                 ser->dev->stats.tx_bytes += tty_wr;
 254
 255                 /* Error on TTY ?! */
 256                 if (tty_wr < 0)
 257                         goto error;
 258                 /* Reduce buffer written, and discard if empty */
 259                 skb_pull(skb, tty_wr);
 260                 if (skb->len == 0) {
 261                         struct sk_buff *tmp = skb_dequeue(&ser->head);
 262                         WARN_ON(tmp != skb);
 263                         if (in_interrupt())
 264                                 dev_kfree_skb_irq(skb);
 265                         else
 266                                 kfree_skb(skb);
 267                 }
 268         }
 269         /* Send flow off if queue is empty */
 270         if (ser->head.qlen <= SEND_QUEUE_LOW &&
 271                 test_and_clear_bit(CAIF_FLOW_OFF_SENT, &ser->state) &&
 272                 ser->common.flowctrl != NULL)
 273                                 ser->common.flowctrl(ser->dev, ON);
 274         clear_bit(CAIF_SENDING, &ser->state);
 275         return 0;
 276 error:
 277         clear_bit(CAIF_SENDING, &ser->state);
 278         return tty_wr;
 279 }
 280
 281 static int caif_xmit(struct sk_buff *skb, struct net_device *dev)
 282 {
 283         struct ser_device *ser;
 284
 285         BUG_ON(dev == NULL);
 286         ser = netdev_priv(dev);
 287
 288         /* Send flow off once, on high water mark */
 289         if (ser->head.qlen > SEND_QUEUE_HIGH &&
 290                 !test_and_set_bit(CAIF_FLOW_OFF_SENT, &ser->state) &&
 291                 ser->common.flowctrl != NULL)
 292
 293                 ser->common.flowctrl(ser->dev, OFF);
 294
 295         skb_queue_tail(&ser->head, skb);
 296         return handle_tx(ser);
 297 }
 298
 299
 300 static void ldisc_tx_wakeup(struct tty_struct *tty)
 301 {
 302         struct ser_device *ser;
 303
 304         ser = tty->disc_data;
 305         BUG_ON(ser == NULL);
 306         WARN_ON(ser->tty != tty);
 307         handle_tx(ser);
 308 }
 309
 310
 311 static int ldisc_open(struct tty_struct *tty)
 312 {
 313         struct ser_device *ser;
 314         struct net_device *dev;
 315         char name[64];
 316         int result;
 317
 318         /* No write no play */
 319         if (tty->ops->write == NULL)
 320                 return -EOPNOTSUPP;
 321         if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_TTY_CONFIG))
 322                 return -EPERM;
 323
 324         sprintf(name, "cf%s", tty->name);
 325         dev = alloc_netdev(sizeof(*ser), name, caifdev_setup);
 326         if (!dev)
 327                 return -ENOMEM;
 328
 329         ser = netdev_priv(dev);
 330         ser->tty = tty_kref_get(tty);
 331         ser->dev = dev;
 332         debugfs_init(ser, tty);
 333         tty->receive_room = N_TTY_BUF_SIZE;
 334         tty->disc_data = ser;
 335         set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
 336         rtnl_lock();
 337         result = register_netdevice(dev);
 338         if (result) {
 339                 rtnl_unlock();
 340                 free_netdev(dev);
 341                 return -ENODEV;
 342         }
 343
 344         list_add(&ser->node, &ser_list);
 345         rtnl_unlock();
 346         netif_stop_queue(dev);
 347         update_tty_status(ser);
 348         return 0;
 349 }
 350
 351 static void ldisc_close(struct tty_struct *tty)
 352 {
 353         struct ser_device *ser = tty->disc_data;
 354         /* Remove may be called inside or outside of rtnl_lock */
 355         int islocked = rtnl_is_locked();
 356
 357         if (!islocked)
 358                 rtnl_lock();
 359         /* device is freed automagically by net-sysfs */
 360         dev_close(ser->dev);
 361         unregister_netdevice(ser->dev);
 362         list_del(&ser->node);
 363         debugfs_deinit(ser);
 364         tty_kref_put(ser->tty);
 365         if (!islocked)
 366                 rtnl_unlock();
 367 }
 368
 369 /* The line discipline structure. */
 370 static struct tty_ldisc_ops caif_ldisc = {
 371         .owner =        THIS_MODULE,
 372         .magic =        TTY_LDISC_MAGIC,
 373         .name =         "n_caif",
 374         .open =         ldisc_open,
 375         .close =        ldisc_close,
 376         .receive_buf =  ldisc_receive,
 377         .write_wakeup = ldisc_tx_wakeup
 378 };
 379
 380 static int register_ldisc(void)
 381 {
 382         int result;
 383
 384         result = tty_register_ldisc(N_CAIF, &caif_ldisc);
 385         if (result < 0) {
 386                 pr_err("cannot register CAIF ldisc=%d err=%d\n", N_CAIF,
 387                         result);
 388                 return result;
 389         }
 390         return result;
 391 }
 392 static const struct net_device_ops netdev_ops = {
 393         .ndo_open = caif_net_open,
 394         .ndo_stop = caif_net_close,
 395         .ndo_start_xmit = caif_xmit
 396 };
 397
 398 static void caifdev_setup(struct net_device *dev)
 399 {
 400         struct ser_device *serdev = netdev_priv(dev);
 401
 402         dev->features = 0;
 403         dev->netdev_ops = &netdev_ops;
 404         dev->type = ARPHRD_CAIF;
 405         dev->flags = IFF_POINTOPOINT | IFF_NOARP;
 406         dev->mtu = CAIF_MAX_MTU;
 407         dev->tx_queue_len = 0;
 408         dev->destructor = free_netdev;
 409         skb_queue_head_init(&serdev->head);
 410         serdev->common.link_select = CAIF_LINK_LOW_LATENCY;
 411         serdev->common.use_frag = true;
 412         serdev->common.use_stx = ser_use_stx;
 413         serdev->common.use_fcs = ser_use_fcs;
 414         serdev->dev = dev;
 415 }
 416
 417
 418 static int caif_net_open(struct net_device *dev)
 419 {
 420         netif_wake_queue(dev);
 421         return 0;
 422 }
 423
 424 static int caif_net_close(struct net_device *dev)
 425 {
 426         netif_stop_queue(dev);
 427         return 0;
 428 }
 429
 430 static int __init caif_ser_init(void)
 431 {
 432         int ret;
 433
 434         ret = register_ldisc();
 435         debugfsdir = debugfs_create_dir("caif_serial", NULL);
 436         return ret;
 437 }
 438
 439 static void __exit caif_ser_exit(void)
 440 {
 441         struct ser_device *ser = NULL;
 442         struct list_head *node;
 443         struct list_head *_tmp;
 444
 445         list_for_each_safe(node, _tmp, &ser_list) {
 446                 ser = list_entry(node, struct ser_device, node);
 447                 dev_close(ser->dev);
 448                 unregister_netdevice(ser->dev);
 449                 list_del(node);
 450         }
 451         tty_unregister_ldisc(N_CAIF);
 452         debugfs_remove_recursive(debugfsdir);
 453 }
 454
 455 module_init(caif_ser_init);
 456 module_exit(caif_ser_exit);